Method of manufacturing stator and rotor cores

ABSTRACT

A tandem press system for the high speed manufacture of rotor cores and stator cores of electric motors. The tandem press system includes a rotor press and a stator press arranged in series for stamping out laminations from a web of stock material and pre-assembling them into rotor cores and stator cores, respectively. Structure is provided between the rotor and stator press to maintain control of the web and provide a substantial barrier to transmission of vibrations in the web to the stator press. The rotor and stator presses are capable of shifting from stamping one type of lamination to stamping another type of lamination without any interruption in the operation of the presses.

This application is a division of application Ser. No. 08/337,626, filedNov. 10, 1994, now U.S. Pat. No. 5,636,432, which is acontinuation-in-part application of Ser. No. 08/139,578, filed Oct. 20,1993.

BACKGROUND OF THE INVENTION

This invention relates generally to tandem press systems and morespecifically to a tandem press system for high speed, flexiblemanufacture of stator and rotor cores of a dynamoelectric machine.

Competitive mass production of dynamoelectric machines in the form ofelectric motors, such as those used in household appliances and othermachines, requires in the manufacture of the motor an emphasis on speedand continuity of operation. Production of stator and rotor cores of themotors has been carried out in a tandem press arrangement in which a webof highly magnetically permeable stock material is fed to a first(rotor) press and then to a second (stator) press. The rotor presspunches out rotor laminations and stacks them in groups to form a rotorcore. Similarly, the stator press punches out stator laminations arounda central opening left by formation of rotor laminations, and stacks thestator laminations into groups to form a stator core.

Among the obstacles to rapid operation is the introduction ofsubstantial vibrations to the web by virtue of the rapid impact andrelease of upper die portions of the presses with the web and, inparticular, the rapid, intermittent feeding of the web. The vibrationsmake it difficult to maintain control of the web to the degree necessaryto prevent misfeed and accurately punch the web. The problem isparticularly acute at the stator press because the web is weakened byremoval of material to form rotor laminations in the rotor press. Theweakened web bends more easily and tends to become hung up in the statordie.

Continuity of operation is interrupted by the need to connect stockmaterial from a new roll to the web as one roll is used up. Furthermore,to manufacture stator cores for one speed and multiple speed motors,either two separate press systems must be employed, or the stator diemust be replaced. Replacement of a die requires a substantial amount ofdown time for the press.

SUMMARY OF THE INVENTION

Among the several objects and features of the present invention may benoted the provision of a tandem press system in which one of the pressesis substantially isolated from vibrations caused by high speed operationof the other press; the provision of such a tandem press system whichprotects the stock material from damage caused by vibration; theprovision of such a tandem press system which is capable of shiftingduring operation from stamping rotor or stator laminations of one typeto stamping rotor or stator laminations of another type; and theprovision of such a tandem press which is capable of consistently andcontinuously producing at high speeds rotor core and stator coresmeeting close tolerances.

Generally, a tandem press system for the high speed manufacture of rotorcores and stator cores of dynamoelectric machines includes a rotor pressfor stamping rotor laminations from a web of stock material and stackinggroups of laminations to form rotor cores, and a stator press forprogressively stamping stator laminations from the remaining stockmaterial in the web after the web leaves the rotor press and stackinggroups of stator laminations to form stator cores. The stator press iscapable of shifting without pause in operation from stamping statorlaminations for one speed motors to stator laminations for two speedmotors. The shifting between stamping stator laminations for one speedmotors and stamping stator laminations for two speed motors iscontrolled by a controller.

Other objects and features of the present invention will be in partapparent and in part pointed out hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic plan view of a tandem press system of the presentinvention including a rotor press and a stator press;

FIG. 2 is a schematic elevation of the tandem press system;

FIG. 3A is a schematic illustration of the progression of formation ofrotor laminations of a first configuration in the rotor press;

FIG. 3B is a schematic illustration of the progression of formation ofrotor laminations at the first, second and fourth stations of the rotorpress and illustrating a second configuration of the rotor laminations;and

FIG. 4 is a partial transverse section of a die set of the rotor pressshowing a movable reaction surface of an upper die portion of the dieset;

FIG. 5 is an enlarged, fragmentary elevation of holding apparatuslocated between the rotor press and stator press;

FIG. 6 is a schematic illustration of the progression of formation ofstator laminations in the stator press;

FIG. 7 is a fragmentary, partial transverse section of a die set of thestator press showing a movable reaction surface of an upper die portionof the die set; and

FIG. 8 is a flow chart showing operation of a tandem press controllerupon start up of the tandem press system.

Corresponding reference characters indicate corresponding partsthroughout the several views of the drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings and in particular to FIGS. 1 and 2, atandem press system of the present invention is shown to comprise arotor press (indicated generally at 20) for stamping rotor laminations R(FIG. 3A) from a web W of highly magnetically permeable stock materialand a stator press (indicated generally at 22) for stamping statorlaminations S (FIG. 6) from the web. In the preferred embodiment, thestock material is a low carbon, low silicon cold-rolled steel, having amaximum carbon content of 0.01%, a maximum silicon content of 0.5% and amaximum aluminum content of 0.25%. The nominal thickness of the stockmaterial is nominally 0.022 inches. It is to be understood that thecomposition and geometry of the stock material may be other thandescribed and still fall within the scope of this invention. A roll L1of the thin, flat stock material is held by a first reel 24 at thebeginning of the tandem press line and let out from the reel in thecontinuous web W through the tandem press system along the pathindicated by dashed lines in FIG. 1. A second reel 26 carrying a secondroll L2 of stock material is provided to facilitate rapid changeoverwhen the roll L1 of material on the first reel 24 is exhausted. The webW extends from the first reel 24 to an accumulator 28 which is capableof receiving and accumulating a quantity of stock material from thefirst reel and letting out the stock material to first web controlmeans, generally indicated at 30, and thence to the rotor press 20. Inthe preferred embodiment, the accumulator is model SCA-7 manufactured byGuild International of Bedford, Ohio. The web W passes from the rotorpress 20 through second web control means, generally indicated at 32,and to the stator press 22.

The rotor press 20 stamps out rotor laminations R and stacks them toform rotor cores (not shown) which are ejected from the side of therotor press onto a rotor core conveyor 34. The rotor laminations Rhaving outer diameters of 3.46 inches (nominally) and inner diameter of0.5004 to 0.5009. The stator press 22 stamps out stator laminations Sand stacks them to form stator cores (not shown) which exit the end ofthe stator press onto a stator core conveyor 36. The stator laminationsS are nominally 5.76 inches square and have an inner diameter ofnominally 3.480. The dimensions of the rotor and stator laminations R, Smay be other than stated herein and still fall within the scope of thepresent invention. The rotor and stator presses 20, 22 are housed in anenclosure 38 which isolates the noise of operation. The operation of thetandem press system is controlled from a control console which at leastpartially houses the tandem press system controller 40. The controller40 may be a single controller or may embody a control circuit for thestator and rotor presses 20, 22 and another circuit for the die sets(described below) within the presses.

A welder 42 movably mounted on rails 44 is disposed between the firstreel 24 of stock material and the accumulator 28 for connecting the endof one roll L1 of stock material to the beginning of another roll L2 ofstock material. An end of roll detector 46 between the welder 42 and thefirst reel 24 detects the end of the stock material roll L1, and causesthe accumulator 28 to automatically stop receiving stock material fromthe direction of the reel 24, but to continue to feed accumulated stockmaterial out to the presses 20, 22. Thus, some of the accumulated stockmaterial in the accumulator 28 begins to be used. The second reel 26 ofstock material is placed in position and a leading edge portion (notshown) is let out from the roll L2 on the second reel 26 to adjacent thetrailing edge portion (not shown) of the prior roll L1 of stockmaterial. The leading and trailing edges may be cut as necessary to forma good joint between the two rolls L1, L2. The welder 42 is moved on thetracks 44 into line with the path of the web W (as shown in FIG. 1) andthe leading edge of the new roll L2 of stock material is welded to thetrailing edge of the prior roll L1 of stock material. The accumulator 28is then activated to draw in stock material in the web W at a ratefaster than it is let out from the accumulator to make up for thereduction in accumulated material let out to the presses 20, 22 duringthe changeover to the new roll L2 of stock material. Thereafter, theaccumulator resumes normal operation in which stock material is fed outat the same rate it is received from the reel 26. In this way, operationof the tandem presses to form stator and rotor cores is not interruptedby changeover to the new roll L2 of stock material.

The first web control means 30 includes a web guide 50, web straightener52 and a first vertical loop stand, generally indicated at 54. Thestraightener 52 is of conventional construction, including a pluralityof feed rollers over which the web W is fed along a generally S-shapedpath to flatten the web which carries the memory of its prior rolledcondition to the straightener. The straightener 52 is capable of feedingout stock material at a slightly higher speed than it is consumed in therotor press 20, and is automatically adjustable to attempt to match thespeed with which stock material is fed into the rotor press. The web Wproceeds from the straightener 52 to a first leg 56 of the firstvertical loop stand 54 which guides the web upward to a second leg 58which guides the web downward and toward the rotor press 20. Between thelegs 56, 58 the web W has an inverted-U shaped section which increasesand decreases in height as the amount of material between the legschanges. Thus, the first vertical loop stand 54 controls the web W whilepermitting variations in speed between the stock material in the web asit enters and exits the first vertical loop stand.

As the web W exits the first vertical loop stand 54 it passes through ameasuring unit 60 which constantly measures the thickness of the stockmaterial. Information as to the thickness of the stock material is usedby the controller 40 to increase or decrease the number of rotor andstator laminations R, L stacked to form rotor and stator cores so thatthe correct heights of the rotor and stator cores are achieved. Inaddition, the controller 40 is capable of changing the number oflaminations R, L in the rotor and stator cores according to instructionspreviously entered into the controller about the run. For instance, aparticular run may call for a certain number of rotor and stator coresof a first height and a certain number having a second height differentfrom the first. The controller 40 is capable of controlling the rotorand stator presses 20, 22 to shift from forming rotor and stator coresof one height to that of another without any pause in operation of thetandem press system.

The rotor press 20 includes a frame having a base 64, a crown portion 66and posts 68 extending up from the base and supporting the crown portionabove the base. The rotor press 20 holds a die set including an upperdie portion 70 and a lower die portion 72. The lower die portion 72 ismounted on a bolster 74 supported on a bed member 76 of the rotor press20, and supports the web W as it passes through the rotor press. Theupper die portion 70 is mounted on a slide 78 that is driven inreciprocation in the space between the crown portion 66 and bed member76 by operation of an electric drive motor 80. A feed device 82 mountedon the rotor press frame receives stock material in the web W from thefirst vertical loop stand and feeds it into the rotor press 20. The feeddevice 82 feeds stock material intermittently, interrupting feed duringthe working stroke of the rotor press 20 when the die set closes andfeeding stock material when the die set is open.

The progressive formation of a rotor lamination R of a first type in therotor press 20 is illustrated schematically by the portion of the web Wshown in FIG. 3A of the drawings. At a station in the rotor press 20which is not illustrated in FIG. 3A, four locator holes H are punched.These holes H are used at later stations in the rotor press 20 andstator press 22 to positively locate the web W using locator pins 84associated with each operating station. At the first station in therotor press 20, punches 86 carried by the upper die portion 70 (shown bycross hatching in FIG. 3A) stamp a series of slots I having angled toeportions T at their radially outer ends. As seen in FIG. 3A, the toeportions T of the slots I in a rotor lamination R of the first type areangled in a counterclockwise direction. Punches 88 at the second station(shown by cross hatching in FIG. 3B) are inactive during formation ofthe first type of rotor lamination R so that no further formation of therotor lamination occurs at the second station.

Similarly the punches (not shown) at the third station are inactiveunless the rotor lamination being formed will be the bottom or firstlamination in a new stack of laminations forming a rotor core. In thatevent, a punch at the third station is active to simultaneously punchthe outer perimeter of the lamination and a center opening C1 of thelamination, as shown in phantom in FIG. 3A. In addition, fourrectangular openings O1 would be formed at the third station to preventthe rotor lamination R from interlocking with the top lamination of theprior stack. However, in most instances the outer perimeter and centeropening C1 are punched by punch 90 at the fourth station as shown insolid lines. In addition, four interlock openings O2 are formed at thefourth station. These openings O2 are punched through, but unlike theopenings O1 the stock material is not removed from the rotor lamination,but remains to form tabs (not shown) which fit into the opening O2 of anadjacent lamination in the rotor core stack to interlock the laminationsin the stack. The details of lamination interlocks are well known tothose of skill in the art. The rotor lamination R, although nowseparated from the web W, is carried by the web to the fifth stationwhere it is pushed by punch 91 into a barrel 92 (illustrated in phantomin FIG. 3A). The barrel 92 is rotated between each working stroke of therotor press 20 so that slight variations in material thickness over therotor laminations R and deviations of the laminations and their centeropenings C1 are substantially cancelled out over the stack oflaminations forming a rotor core. In this way, highly accurate rotorcores are produced.

The rotor core is formed by a stack of rotor laminations R of the firsttype (described above) and rotor laminations R' of a second type. In apreferred embodiment, the rotor core is formed by a stack including twosets of rotor laminations of one type (R or R') with one set of rotorlaminations of the other type disposed between them. The web W at thefirst, second and fourth stations of the rotor press 20 during formationof rotor laminations R' of the second type is shown in FIG. 3B. To formrotor laminations R' of the second type, the punches 86 at the firststation are inactive, and the now active punches 88 at the secondstation form slots I' with toe portions T' angled in a clockwisedirection (i.e., in a direction opposite the toe portions of rotorlamination slots of the first type). A rotor core is formed by stackingat least one set of rotor laminations R of the first type and anotherset of rotor laminations R' of the second type. This compound formationof the rotor core produces an alignment of slots I, I' defining passages(not shown) through the length of the rotor core which are partiallyskewed as a result of the toe portions T, T'. These passages are laterfilled with an electrically conductive material to form induction barsof the rotor core. A more detailed description of the rotor core soformed may be found in co-assigned U.S. application Ser. No. 08/139,578,filed Oct. 20, 1993, the disclosure of which is incorporated herein byreference. However, it is to be understood that the rotor press 20 neednot be configured to from rotor cores using a straight skew design asdescribed above to fall within the scope of the present invention. It isenvisioned that the die set in the rotor press 20 could be configured tostamp rotor indication bar slots of a single type and achieve a spiralskew by rotation of each lamination in the stack relative to theadjacent laminations.

As shown in FIG. 4, the lower die portion 72 of the rotor press 20includes a main body 94 having an opening 96 for ejection of scrappunched from the web W. A first insert 98 is received in recess in themain body 94 and underlies a second insert 100 received in a die member102 mounted on the upper surface of the main body. Web guides 104secured to the die member 102 at laterally spaced apart locations guidethe web W through the rotor press 20. The second insert 100 has aplurality of holes in which are received third inserts 106 havingopenings shaped in the form of the rotor lamination slots I of the firsttype. These openings receive the tips of the punches 86 at the bottom ofthe working stroke of the rotor press 20 and define the surface againstwhich the web W is punched to form the slots I. The third insert 106 ismade of carbide and forms the cutting surface of the lower die portion72.

The upper die portion 70 at the first station in the rotor press 20carries a plurality of the punches 86 (only two of which are shown)secured to a guide plate 108 by a generally circular retainer plate 110.The retainer plate 110 is received at its periphery in notches in eachpunch 86 and secured to the guide plate 108 by bolts (not shown). Abridge stripper 112 is secured by clamps (not shown) to the main body 94on top of the web guides 104, and has through holes which receive thedistal end portions of the punches 86. The bridge stripper 112 holdsdown the web W and removes it from the punches 86 after each workingstroke of the rotor press 20. The bridge stripper 112 is advantageous inthat it is not mounted on the upper die portion 70, and therefore doesnot add its mass to the inertia of the upper die portion. However, it isenvisioned that other types of strippers, such as spring strippers (notshown) could be used and still fall within the scope of the presentinvention. The guide plate 108 is mounted on a backing plate 116received in a recess in a main body 118 of the upper die portion 70 andengaging the upper ends of the punches 86. The backing plate 116 issecured in the recess by bolts 120 and lugs 122 (only one set is shown).A guide pin 124 is received through the main body 118, backing plate 116and guide plate 108 for maintaining the proper alignment between theseelements. The guide pin 124 is received in a bushing 126 in the backingplate 116 which permits vertical movement between the guide plate andthe main body 118. A pusher bar 128 supported on a spring (schematicallyindicated at 130) in a hole in the main body 94 of the lower die portion72 extends upward through the die member 102 and bridge stripper 112.The pusher bar 128 engages the guide plate 108 only at near the bottomof the working stroke of the rotor press 20. The pusher bar 120 andspring 130 prevent the punches 86 from engaging the web W when the firststation is inactive, as described more fully below.

Activation and de-activation of the punches 86, 88 forming the slots I,I' of the first and second types respectively in the rotor laminationsR, R' is achieved without interruption of the operation of the rotorpress 20. A reaction surface member 132 is mounted in the main body 118of the upper die portion 70 for sliding motion laterally of the backingplate 116 by operation of a pneumatic cylinder 134 carried by the mainbody and connected to the reaction surface member by link bar 136. Thereaction surface member 132 has a plurality of teeth 138 on its bottomsurface which, when the reaction surface member is in the punch position(as shown in FIG. 4), are in registration with and engage similarlyformed teeth 140 on the upper surface of the backing plate 116. Thereaction surface member 132, when in the punch position shown in FIG. 4,holds the backing plate 116, and hence the punches 86, from verticallyupward motion relative to the main body 118. Thus when the punches 86strike the web W, slots I of the first type are formed in the web.However, if the cylinder 134 is activated to rapidly slide the reactionsurface member 132 to a release position so that the teeth 138, 140 ofthe reaction surface member and backing plate 116 move out ofregistration, the backing plate and punches 86 will move up under theurging of spring 130 and pusher bar 128 on the working stroke. The teeth140 on the backing plate are received between the teeth 138 on thereaction surface member 132. Slots I will not be formed and the firststation becomes inactive. More specifically, when it is desired to forminduction bar slots I' of the second type, the reaction surface member132 is moved to the release position thereby rendering the first stationof the rotor press 20 inactive. Simultaneously, a substantiallyidentical reaction surface member (not shown) at the second station ismoved to the punch position to activate the second station. Thechangeover from active punching at the first station to active punchingat the second station occurs within one stroke of the rotor press 20 sothat there is no interruption in reciprocation of the press. Theselective operation of the punch (not shown) at the third station andpunch 90 at the fourth station is achieved with substantially the samestructure as described above for the first station.

The web W exiting the rotor press 20 passes through a second verticalloop stand (indicated generally at 142) having a first leg 144 and asecond leg 146. As shown in FIG. 5, each leg 144, 146 has web pathdefining members 148, made of nylon or other suitable low-frictionmaterial, which guide the web W along a path which does not extend backupon itself. More specifically, the portion of the web W in the secondvertical loop stand 142 (broadly, "holding apparatus") assumes agenerally inverted-U shape which helps to inhibit creasing of the stockmaterial in the web caused by folding of the stock material back uponitself as a result of the vibrations introduced to the web by theintermittent feed of the web and the high speed reciprocation of therotor press 20.

However, it has been found that in vibrations introduced by the highspeed operation of this tandem press system can still cause creases inthe stock material. Between the first and second legs 144, 146 is agenerally rectangular spring steel member 150 which is fixedly attachedat one end 150A to the first leg and attached to the second leg at itsopposite end 150B for vertical sliding motion relative to the secondleg. The web W passes over and is supported by the spring steel member150 between the legs 144, 146. The spring steel member 150 permits thetop of the loop of the web W in the second vertical stand 142 to move upand down while tending to hold the top of the loop in a smooth,inverted-U form. The spring steel member 150 increases or decreases itslength between the first and second legs 144, 146 by the sliding actionof the end 150B of the member slidably connected to the second leg. Toincrease the ability of the spring steel member 150 to follow the rapidmovements of the web W, a pair of cylindrical rollers 152 extendingtransversely of the web engage the underside of the spring steel member.The rollers 152 are mounted at each end in a vertical slot 154 in aframe 156 mounted between the first and second legs 144, 146. The endsof each roller 152 are each connected to one end of a spring 158, theother end of which is connected to the nearest of the first and secondlegs 144, 146. Only one of the two springs 158 is shown for each rollerin FIG. 5. The spring mounted rollers 152 bias the spring steel member150 generally upwardly, permitting it to react quickly with themovements of the web W to maintain engagement with the web and to holdit in its smooth, inverted-U shape between the legs 144, 146 of thestand 142.

As it leaves the second vertical loop stand 142, the web W is stillsubject to substantial vibratory action as a result of the rotor press20. In order to maintain control of the web W to a degree needed foroperations on the web in the stator press 22, a web straightener 160located after the second vertical loop stand 142 provides a barrier topropagation of vibrations in the web to the stator press (FIG. 2). Thestraightener 160 firmly grips the web W to substantially reduce thevibrations. The straightener 160 is not used in this context for itsordinary function of removing a prior configuration of the web Wretained in its elastic memory. Although a straightener 160 has beenfound to provide a satisfactory barrier to vibrations, it is envisionedthat other mechanisms which firmly grip the web W could be used withoutdeparting from the scope of the present invention.

As shown in FIG. 2, the stator press 22 includes a frame comprising abase 161, a crown portion 162 and posts 163 extending up from the baseand supporting the crown portion above the base. The stator press holdsa die set including an lower die portion 178 and an upper die portion180. The lower die portion 180 is mounted on a bolster 165 supported ona bed member 167 of the stator press, and supports the web W as itpasses through the stator press 22. The upper die portion 180 is mountedon a slide 169 that is driven in reciprocation in the space between thecrown portion 162 and the bed member 167 by operation of an electricdrive motor 171. A feed device 173 mounted on the stator press framereceives stock material in the web W from the web straightener 160 andfeeds it to the stator press 22. The feed device 173 feeds stockmaterial intermittently, interrupting feed during the working stroke ofthe stator press 22 when the die set closes, and feeding stock materialwhen the die set is open.

Referring now to FIG. 6, a progression of the web W through the statorpress 22 for forming a stator lamination S for a two speed motor isshown. At the first station, stator slot deepening punches 164A(illustrated by cross hatching in FIG. 6) stamp a generallysemi-circular array of openings in the web W around a central opening C2in the web W left by formation of the rotor laminations R, R'. At thesecond station, other stator slot deepening punches 164B stamp anopposing generally semi-circular array of openings. Together, the twosemi-circular arrays of punches 164a, 164B constitute "the second set"of punches in this embodiment. One speed stator slot punches 166 (e.g.,a "first set" of punches) at the third station form slots in the web Waround the central opening sufficient to accommodate the windings of aone speed motor. However, the openings stamped by the slot deepeningpunches 164A, 164B deepen certain of these slots so that slots A neededto accommodate the windings for a two speed motor are formed. Thelocator holes H previously formed in the rotor press 20 are subsumedwithin certain slots formed by the one speed slot punches. The slots Aare not entirely completed at the third station as they do not yet openinto the central opening C2 of the stator lamination S.

The fourth station is activated only for punching rectangular openingsO3 in the bottom stator lamination of each stator core formed in thestator press 22. The openings O3 are punched clean (just as openings O1in the rotor laminations R, R') so that the top stator lamination in theprior stator core which not interlock with the bottom stator laminationof the new stator core. The slots A are opened to the central opening C2at the fifth station by a center opening punch 169 at the same timerecesses are formed by corner punches 170 at the four corners of thelamination S which will form a channel receiving a fastener (not shown)which connects the stator laminations together. If the fourth station isinactive, the interlock punches (not shown) at the fifth station punchopenings O4 and interlock tabs which are received in openings O4 ofadjacent stator laminations in the stack to interlock the laminations.The sixth station is idle because of space requirements in the statorpress 22 for the fifth station and the seventh station. The statorlamination S is punched away from the web W at the seventh station andinto a barrel 174 (shown in phantom) similar to the barrel 92 of therotor press 20. The rotation of the barrel 174 is controlled by amechanical indexer (not shown) connected to the barrel by a cogged belt176 for rotating the barrel 90° after each lamination S is depositedinto the stack forming the stator core in the barrel. The mechanicalindexer is preferably model 17D-0227-2 mechanical indexer manufacturedby Sankyo of Japan and available in this country through Sankyo America,Inc. of Sidney, Ohio.

The formation of one speed motor stator laminations (not shown) issubstantially the same as described for formation of two speed motorstator laminations S, except that the slot deepening punches 164A, 164Bat the first two stations are inactive. As shown in FIG. 7, this isaccomplished in a way substantially identical to the deactivation ofpunches 86 in the rotor press 20. In that regard, the stator press 22has a die set including a lower die portion 178 adapted to support theweb W as it passes through the stator press, and an upper die portion180 mounted for reciprocating motion above the lower die portion. Webguides 182 mounted on an upper surface of a main body 184 of the lowerdie portion 178 guide the web W through the stator press 22. A bridgestripper 186 secured to the main body 184 and located above the webguides 182 holds the web W in place and strips the web off the punches164A (only two of which are shown) after the end of the working strokeof the stator press 22.

Openings in the bridge stripper 186 receive the lower ends of the slotdeepening punches 164A and permit access of the punches to the web W.The upper ends of the punches 164A are received in a guide plate 188 andheld therein by lugs 190 received in notches in the punches 164A andattached by bolts 192 to a backing plate 194. The backing plate 194 ismounted on a main body 196 of the upper die portion 180 above thepunches 164A. A first guide pin 198 passing through the main body 196,backing plate 194 and guide plate 188 maintains alignment between theseelements of the upper die portion 180. The first guide pin 198 isreceived in a bushing 200 the backing plate 194 to permit verticalmotion of the backing plate relative to the bushing and main body 196. Asecond guide pin 202 depends from the guide plate 188 and passes throughthe bridge stripper 186 and main body 184 of the lower die portion 178,thereby maintaining an alignment between these elements of the die set.

The upper surface of the backing plate 194 is formed with teeth 204which, as shown in FIG. 7, are in registration with and engaging teeth206 formed on the lower surface of a reaction surface member 208 abovethe backing plate. The reaction surface member 208 is mounted in themain body 196 for sliding motion laterally of the body above the backingplate 194. The motion is powered by a cylinder (not shown, butsubstantially identical to cylinder 134 of the rotor press 20) connectedto the reaction surface member by a link bar 210. The controller 40 iscapable of operating the cylinder for movement of the reaction surfacemember 208 between a punch position in which the teeth 204, 206 of thebacking plate 194 and reaction surface member are in registration (asshown in FIG. 7) and a release position in which the teeth 204, 206 ofthe backing plate and reaction surface member are out of registration.In the punch position, the reaction surface member 208 holds the backingplate 194 and rigidities the punches 164A for punching through the web Wat the bottom of the working stroke of the stator press 22. In therelease position, the backing plate 194 and punches 164A are permittedto move upward upon engagement with the stock material in the web W sothat no openings are formed in the web. The teeth 204 of the backingplate 194 are received between the teeth 206 of the reaction surfacemember 208. The change in from the punch position to the releaseposition occurs within a single stroke of the stator press 22 so thatthere is no interruption in operation of the press when changing fromforming one speed stator laminations to two speed stator laminations S.Thus, not only is there no requirement for changing the die set in thestator press 22 to form stator laminations for different speed motors,there is not even any interruption in the operation of the stator press.

Rapid operation of the tandem press system (i.e., in excess of 400strokes per minute) produces vibrations in the web W by the rapid impactand release of the stator and rotor press upper die portions 70, 180,and also produces undesirable jerking in the web caused by theintermittent feed of the web to the presses 20, 22 by the feed devices60, 173. To reduce jerking of the web W caused by rapid starts and stopsbecause of the intermittent feed, controller 40 operates press 20 andstator press 22 at substantially the same speed and out of phase witheach other. Thus, the feeding cycles for each press are different givingthe web W a smoother travel through the presses. More specifically, therotor press 20 is set to run out of phase and ahead of stator press 22by about 65° to 85° (based on a 360° mechanical cycle). More preferably,the phase difference is set to be between about 70° and 80°, and mostpreferably at about 70°. The phase differential is achieved byelectronically presetting the top stop position of each press.

Rapid operation of the rotor and stator presses 20, 22 also requirescareful monitoring of the relative speed of the presses so that theproper speed synchronization is maintained. Of course, it is to beunderstood that the rotor press 20 and stator press 22 desirably operateout of phase, but that it is important to synchronize their operationsat the selected out of phase condition. In other words, synchronizingthe presses 20 and 22 is defined as operating the presses atsubstantially the same speed and out of phase at a preselected angle.Maintenance of synchronization is particularly difficult when thepresses are accelerating as during start up of the tandem press system.The controller 40 has start up means (in this embodiment a dedicatedhardwired logic circuit within controller 40) for controlling start upof the presses 20, 22. The start up means may also be implemented bysoftware or in the form of a programmable logic array (PLA). The startup means of controller 40 executes the flow chart of FIG. 8. Initially,at step 220, the start up means activates reciprocation of the presses.Next, step 222 is executed to accelerate the presses toward apreselected full operating speed at a first controlled accelerationrate. During this initial ramp up, a comparator within the start upmeans executes step 224 and compares the speed signal of the statorpress 22 to the speed signal of the rotor press 20 and a signal isgenerated to increase or decrease the speed of the stator press asneeded to maintain synchronization.

At a plateau value (e.g., 140 strokes per minute) the start up means inthe controller 40 halts the acceleration of the rotor press 20 andstator press 22 for a predetermined period of time to permit the startup means to substantially converge and synchronize the speeds of therotor press and stator press. In the preferred embodiment, a dwell ofapproximately 45 seconds is satisfactory to reestablish synchronization.Start up means executes step 228 to determine if the plateau value hasbeen reached. If the speed of both presses is below the plateau value,the start up means returns to step 222 and continues acceleration. Ifthe speed of either press is above the plateau value, loop 230 isexecuted to discontinue further acceleration until the presses areresynchronized. At step 232, a dwell timer is started to time the dwellperiod during which the acceleration will be discontinued. Steps 234 and236, which correspond to steps 224 and 226, continue to be executed aspart of loop 230. In addition, step 238 is executed at the end of eachloop 230 to determine if the dwell timer has timed out or equals thedwell period. If it has not, loop 230 is again executed.

When the dwell timer equals or exceeds the dwell period, start up meansexecutes step 240 to reaccelerate the reciprocation from the plateauspeed at a second controlled acceleration rate (e.g., 100 strokes perminute²) slower than the first controlled acceleration rate to achievethe full desired operating speed. At steps 242 and 244, the start upmeans continues to compare the speeds of the presses and makecorresponding speed and phase changes to maintain synchronization aslong as the tandem press system is in operation. If the full operatingspeed is achieved, the start up means returns to step 242 to continuespeed and phase control. If the full operating speed is not achieved,the start up means returns to step 240 to continue reacceleration aswell as speed and phase control.

In view of the above, it will be seen that the several objects of theinvention are achieved and other advantageous results attained.

As various changes could be made in the above constructions withoutdeparting from the scope of the invention, it is intended that allmatter contained in the above description or shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

We claim:
 1. A method for high speed formation of stator laminations foruse in a dynamoelectric machine from a web of steel material, the methodcomprising the steps of:delivering the web of material to the statorpress; activating a set of slot-deepening punches in the stator pressdie to stamp slot-deepening openings in the web, the slot deepeningopenings being spaced apart with none of the slot-deepening openingsintersecting any of the other slot-deepening openings; stamping primaryslots in the web with another set of punches carried by the stator pressdie, selected ones of said primary slots communicating withcorresponding ones of the slot-deepening openings, to form slots of thestator lamination, the slots being sized and shaped for receivingwindings of the dynamoelectric machine.
 2. A method as set forth inclaim 1 wherein said primary slots, as unmodified by the openings, aresized and shaped to receive the windings of an electric motor having afirst number of speeds, and wherein the slots formed by the primaryslots, including those communicating with the slot-deepening openings,are sized and shaped for receiving the windings of an electric motorhaving a second number of speeds different from the first.
 3. A methodfor high speed, selective formation of stator laminations for a statorcore of a motor having a first number of speeds and stator laminationsfor a stator core of a motor having a second number of speeds differentfrom the first, the stator laminations being stamped from a web ofhighly permeable magnetic material, the method comprising the stepsof:delivering the web of magnetic material to a reciprocating statorpress; providing a first set of punches fixed in a die of the statorpress for stamping a generally circular array of first slots around acenter of the lamination on every working stroke of the stator press,the first slots extending generally radially outwardly from the center,any stator lamination formed with the first slots being capable ofreceiving in the first slots windings for the motor having the firstnumber of speeds; selectively activating and deactivating a second setof punches in the stator press die without interrupting thereciprocating motion of the stator press, the second set of punches,when activated, stamping slot-deepening openings in the web, at leastsome of the first slots communicating with the slot-deepening openingsto form elongated slots to produce stator laminations capable ofreceiving windings for the motor having the second number of speeds, thesecond set of punches, when deactivated, refraining from stamping theslot-deepening openings so that the stator press produces statorlaminations capable of receiving the windings of the motor of the firstnumber of speeds.
 4. A method as set forth in claim 3 wherein the stepof selectively activating the second set of punches occurs before thefirst slots are stamped in the web.
 5. A method as set forth in claim 3wherein the step of activating the second set of punches is carried outby an electronic control circuit preprogrammed with customer orders formotors having the first number of speeds and motors having the secondnumber of speeds, the electronic control circuit activating anddeactivating the second set of punches without interruption or slowingdown reciprocation of the stator press to produce stator laminations formotors having the first number of speeds and stator laminations ofmotors having the second number of speeds.
 6. A method as set forth inclaim 3 wherein the step of activating the second set of punchescomprises the step of activating a cylinder to move a reaction surfacemember on the stator press die between a punch position in which thereaction surface member holds said second group of punches for punchingthrough the web of material and a release position in which the reactionsurface member releases said second set of punches to prevent punchingthrough the web.